Nonlinear control of a benchmark beam balance experiment using variable hyperbolic bias

Magnetic bearing control schemes frequently use a bias current together with a superimposed control current to improve actuator gain and linearity. In this paper a variable bias scheme is developed to reduce electrical power loss while maintaining the control performance similar to conventional bias control. Two different bias schemes are proposed: a linear bias scheme and a hyperbolic bias scheme. A bias-dependent feedback linearization approach is applied to both systems to make the input/output relation of the system linear, and an observer-based stabilizing controller is designed to stabilize the nominal closed loop system. The resulting closed loop system dynamics are independent of bias except for amplifier saturation. The bias is minimized while avoiding amplifier saturation and singularity in feedback linearization with a separate bias control loop